Читать книгу Lessons in Wireless Telegraphy онлайн

4 страница из 17

FIG. 3. Lodestone suspended from thread so as to point North and South.

Furthermore, if the poles of the suspended magnet are marked so as to easily be identified it will be found that it is always the same pole that swings towards the north. There would therefore appear to be two kinds of magnetism or at least two kinds of magnetic poles. The end swinging toward the north is termed the "north seeking pole" and the opposite end called the "south seeking pole." In common parlance they are simply termed the North and South poles. It is usual to mark the North Pole with the letter N.

There is no known insulator of magnetism: it passes through everything. A magnetic substance is one which offers little resistance to the field of force.

Magnetism flows along certain lines called Lines of Magnetic Force. These lines always form closed paths or circuits. The region in the neighborhood of a magnet through which these lines pass is called the Field of Force and the path through which they flow is called the Magnetic Circuit.